Gold-chlorine interactions

A related dinuclear species 77, recently described, constitutes the first dinuclear gold(I) complex with heterobridged phosphor-1,1 -dithiolato moieties and bis(ylide) bridging ligands [ 102]. It is obtained by reaction between [ AuS2PPh2] and the diylide gold complex 74 (R=Me). No intermolecular Au-Au interaction is observed in 77 but the oxidative addition of chlorine to the product leads to a new complex 78 in which a single bond is formed between the two Au(II) centers (Scheme 26). 

Halides. Gold(III) chloride [13453-07-1] can be prepared directly from the elements at 200°C (167). It exists as the chlorine-bridged dimer, Au2Q6 in both the solid and gas phases under an atmospheric pressure of chlorine at temperatures below 254°C. Above this temperature in a chlorine atmosphere or at lower temperatures in an inert atmosphere, it decomposes first to AuCl [10294-29-8] and then to gold. The monochloride is only metastable at room temperature and slowly disproportionates to gold(0) and gold(III) chloride. The disproportionation is much more rapid in water both for AuQ and the complex chloride, [AuClJ, formed by interaction with metal chlorides in solution. 

As we discussed, numerous neutrinos are produced by the proton-proton chain in the Sun. However, neutrinos interact only very weakly with matter. Every second over 100 billion neutrinos from the Sun pass through every square inch of our bodies and virtually none of them interact with us. Because neutrinos interact so weakly with matter, detecting them is very difficult. For example, in the first solar neutrino detection experiment, scientist Ray Davis used 100,000 gallons of cleaning fluid (for the chlorine the fluid contained) in a detector located in a South Dakota gold mine. Davis expected to detect on average of 1.8 solar neutrinos per day. Instead, Davis s observed rate has consistently been much lower than this. Also, the long-term rate, plotted as a function of time, shows an anticorrelation between neutrino rate and sunspot activity. 

Similar to (SN), in their one-dimen.sional conductivity properties are the stacked columnar complexes typified by [Pt(CN)4] . These. square planar ions adopt a closely spaced parallel arrangement, allowing for considerable interaction among the d.2 orbitaLs of the platinum atoms. These orbitals are normally filled with electrons,. so in order to get a conduction band some oxidation (removal of electrons) must take place. This may be readily accomplished by adding a little elemental chlorine or bromine to the pure tetracyanoplatinate salt to get stoichiometries such as K2[Pt(CN)4]Br in which the platinum has an average oxidation state of +2.3. The oxidation may al.so be accomplished electrolytically. as in the preparation of Rb2[Pt(CN)4](FHF)o4 (Fig. 16.8), which has a short Pt—Pt separation. The Pt—Pt distance is only 280 pm. almost as short as that found in platinum metal itself (277 pm) and in oxidized platinum pop complexes (270 to 278 pm see Chapter l5).- 2 Gold-bronze materials of this type were discovered as early as 1842, though they have been little understood until recent times. The complexes behave not only as one-dimensional conductors, but... 

In Table 1 the gold contents deposited on the Pt surface are reported. This method of preparation allows to obtain bimetallic catalysts in which the two metals are in close interaction. It can be seen the addition of a very low load of gold decreases the accessibility of Pt in a significant way. The Pt accessibility decreases with gold content. To avoid the chlorine role in catalytic properties, the chloride contents are also reported in Table 1, and was almost the same for all bimetallic catalysts. 

The characterization results of the Au/Pd/y-Al203 samples are given in Table 3. They show that similar loadings of gold were deposited whatever the method used. In addition, no chlorine was detected by XPS on any sample. A tentative explanation for this differential behaviour of the two samples might invoke differences in the interaction of palladium particles with the gold species, which would be related to the nature of the gold complexes effectively present on the catalyst surface. 

Annibale and coworkers have reported a kinetic study of the reduction of Au(III) to Au(I) by various dialkyl sulfides. In their evaluation of the reactions, the authors concluded (0 The first step of the interaction establishes the substitution equilibria (h) The second step involves transfer of a chlorine atom from Au(III) to free sulfide. This leads to a digonal gold(l) complex and a halosulfonium salt, [R2SC1]C1, as the primary reaction products. Scheme 9.5 ... 

Figure 12.6 (a) Fourier-transformed gold tm EXAFS of the reaction of potassium tetrachloroaurate with a wheat biomass at pH 3, showing the presence of chlorine ligands and gold-gold interactions (b) Fourier-transformed gold till EXAFS of the reaction of potassium tetrachloroaurate with an amine... 

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